Project Summary In most low- and middle-income countries (LMICs), more children are surviving into adulthood affected by the developmental sequelae of early illness, undernutrition and adverse experiences. In rural Guatemala, where the proposed study would take place, the number of infants at risk for impaired development is among the highest in the world, due to high rates of undernutrition, poverty, and limited preventive health care. To identify and target services to infants at children at risk, most community programs rely on basic growth indicators or parent- reported concerns, techniques which are indirect measures of development and not sensitive in infancy. As a result, data on the onset of developmental disabilities in infants are almost completely missing, and early interventions are begun well after significant adverse effects have already occurred. Technologies to support earlier identification of atypical development would therefore support earlier intervention and improved neurodevelopmental outcomes. As limb movements are one of the earliest outputs of the developing central nervous system, the novel response to this early identification challenge proposed here is to quantitatively differentiate typical and atypical early limb movement patterns in infants at risk for developmental disability due to stunting in rural Guatemala using wearable motion sensors. The first aim of this project is to determine the relationship between infants? earliest spontaneous limb movements and developmental outcomes at 12 months in infants at risk using wearable motion sensors. The second aim of this project is to determine whether wearable sensor assessment is more accurate than current clinical assessments in predicting developmental outcomes in infants at risk. Taken together, our work addresses the need for novel approaches for infants with atypical neurodevelopment due to undernutrition and other risk factors. We will conduct this work in rural Guatemala, which has one of the highest rates of these infant risk factors in the world. Our results have the potential to improve quality of life and health outcomes for Guatemalans and other LMIC citizens through earlier identification of atypical development, supporting earlier intervention and improved neurodevelopmental outcomes. Further, this exploratory/developmental research application is a multidisciplinary capacity-building project involving pediatric medicine, physical therapy, and biostatistics. The project will build research capacity in Guatemala, through a partnership between the University of Southern California (a U.S. institution) and Maya Health Alliance (an LMIC institution). The proposed research plan will strengthen the research capabilities at the LMIC institution and in Guatemala, specifically through training of local healthcare staff and PhD students in conducting neurodevelopmental assessments in infants, a critical need given the high local prevalence of developmental disability and stunting.